Tunable resonator

ABSTRACT

A resonator device includes a substrate with a first number of fins extending over the substrate. The fins extend along the substrate in a first direction. A second number of conductive fingers are provided over the fins, which extend in a second direction perpendicular to the first direction. The first number is less than or equal to the second number. The conductive fingers are configured to receive an input signal such that the conductive fingers resonate at an output frequency. The conductive fingers define a finger pitch therebetween, and the output frequency is based on the finger pitch.

BACKGROUND

Electronic circuits typically include a clock circuit. Such clockcircuits may provide one or more timing signals to the electroniccircuit. The clock circuit is generally implemented via an integratedcircuit and in certain examples may utilize complementarymetal-oxide-semiconductor (CMOS) technology. Clock circuits generallyinclude an oscillator and a resonator. An oscillator may include anelectric circuit that produces a periodically varying output at acontrolled frequency. Filters may be implemented in circuits thatselectively pass certain elements of a signal while eliminating otherelements of the signal. A resonator may include circuitry that exhibitsresonant behavior (i.e., naturally oscillates at resonant frequencieswith greater amplitude than at other non-resonant frequencies).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion. In addition, the drawings are illustrative as examples ofembodiments of the invention and are not intended to be limiting.

FIG. 1 is a block diagram illustrating an example of a resonator devicein accordance with some embodiments.

FIG. 2 is a schematic diagram illustrating an example of portions of aresonator device in accordance with some embodiments.

FIG. 3 is a schematic diagram illustrating an example of portions of aresonator device in accordance with some embodiments.

FIG. 4 is a schematic diagram illustrating an example of additionalportions of a resonator device in accordance with some embodiments.

FIG. 5 is a flow diagram illustrating an example method of fabricating aresonator in accordance with some embodiments.

FIG. 6 is a schematic diagram illustrating an example of fins of aresonator device in accordance with some embodiments.

FIG. 7 is a schematic diagram illustrating an example of fins andconductive fingers of a resonator device in accordance with someembodiments.

FIG. 8 is a schematic section view taken along line Y2 of FIG. 4 inaccordance with some embodiments.

FIG. 9 is a schematic section view taken along line X2 of FIG. 4 inaccordance with some embodiments.

FIG. 10 is a schematic section view taken along line Y1 of FIG. 4 inaccordance with some embodiments.

FIG. 11 is a schematic section view taken along line X1 of FIG. 4 inaccordance with some embodiments.

FIG. 12 is a circuit diagram illustrating an example resonator circuitin accordance with some embodiments.

FIG. 13 is a circuit diagram illustrating another example resonatorcircuit in accordance with some embodiments.

FIG. 14 is a schematic diagram illustrating an example of a conductivefinger arrangement of a resonator device in accordance with someembodiments.

FIG. 15 is a schematic diagram illustrating another example of aconductive finger arrangement of a resonator device in accordance withsome embodiments.

FIG. 16 is a schematic diagram illustrating another example of aconductive finger arrangement of a resonator device in accordance withsome embodiments.

FIG. 17 is a schematic section view illustrating metal layers of aconductive finger arrangement of a resonator device in accordance withsome embodiments.

FIG. 18 is a schematic section view illustrating further aspects ofmetal layers of a conductive finger arrangement for a resonator devicein accordance with some embodiments.

FIG. 19 is a schematic section view illustrating further aspects ofmetal layers of a conductive finger arrangement for a resonator devicein accordance with some embodiments.

FIG. 20 is a schematic section view illustrating further aspects ofmetal layers of a conductive finger arrangement for a resonator devicein accordance with some embodiments.

FIG. 21 is a schematic section view illustrating varying finger pitch ofa conductive finger arrangement for a resonator device in accordancewith some embodiments.

FIG. 22 is a schematic section view illustrating further varying fingerpitch of a conductive finger arrangement for a resonator device inaccordance with some embodiments.

FIG. 23 is a schematic diagram illustrating a multiple resonator cellarrangement for a resonator device in accordance with some embodiments.

FIG. 24 is a schematic diagram illustrating another multiple resonatorcell arrangement for a resonator device in accordance with someembodiments.

FIG. 25 is a schematic diagram illustrating another multiple resonatorcell arrangement for a resonator device in accordance with someembodiments.

FIG. 26 is a schematic diagram illustrating another multiple resonatorcell arrangement for a resonator device in accordance with someembodiments.

FIG. 27 is a schematic diagram illustrating another multiple resonatorcell arrangement for a resonator device in accordance with someembodiments.

FIG. 28 is a flow diagram illustrating an example resonator method inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature’s relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A clock circuit is a basic building block many electronic circuits,including high-speed and radio frequency (RF) integrated circuits (ICs).Such clock circuits provide one or more timing signals to the associatedcircuits. Clock circuits generally include an oscillator and aresonator. An oscillator may include an electric circuit that produces aperiodically varying output at a controlled frequency. Filters may beimplemented in circuits that selectively pass certain elements of asignal while eliminating other elements of the signal. A resonator mayinclude circuitry or structure that exhibits resonant behavior (i.e.,naturally oscillates at resonant frequencies with greater amplitude thanat other non-resonant frequencies). Oscillators, filters, resonators andthe like may use quartz crystal, inductors, and/or capacitors togenerate or promote certain signal frequencies. In ICs, a high frequencyclock may be generated by an off-chip crystal together with an on-chipfrequency doubler, an on-chip LC oscillator, an on-chip ring oscillator,and the like. For such clock circuits, improvements in parameters suchas power reduction, improved performance, and reduced chip area aredesired.

Clock circuits may be implemented using complementarymetal-oxide-semiconductor (CMOS) technology. With certain oscillatorcircuits implemented using CMOS technology, frequency tuning isunavailable. For example, a fin field-effect transistor (FinFET) is amultigate device - a MOSFET (metal-oxide-semiconductor field-effecttransistor) built on a substrate where the gate is placed on two, three,or four sides of the channel or wrapped around the channel. Thesource/drain (S/D) regions of these transistors are formed by fins on orover the substrate surface. Some known CMOS resonator devices employresonant body transistor structures, though the frequency of suchdevices is not tunable. Others use the semiconductor fins of FinFETtransistors to form a mechanical resonator structure. In these devices,the fin pitch determines the resonator frequency. Since the fin pitch isnot variable in such CMOS resonator structures, they do not providetunable output frequency.

However, in some circuit implementations, it may be desirable for thefrequency output of clock circuits to be tunable. Some disclosedexamples provide a resonator structure based on CMOS structures usingstandard CMOS technology, such as a CMOS transistor structure. Somedisclosed embodiments use conductive fingers (i.e. gate strips) ofFinFET transistor structures to form a resonator structure. A “fingerpitch” of conductive strip structure may be varied to define oscillationfrequency of the resonator structure, rather that the fin pitch of avertical fin structure. Further, in some examples, the S/D region of aresonator drive fin structure includes a dielectric material, such asoxide, such that these regions of the fins do not form S/D regions. Inother words, in some examples, the drive FinFET finger structure doesnot function as a transistor. As such, disclosed examples provide aresonator structure with a tunable frequency, and that is alsocompatible with standard CMOS processes.

More particularly, some examples of the tunable resonator includes ahorizontal finger structure, where the resonator frequency is based onthe pitch of the horizontal finger structure. Some examples have afinger pitch range from 1 nm to 1000 nm. Further examples have a fingerpitch of 90 nm to 130 nm, though other finger pitch dimensions arewithin the scope of this disclosure. Further, while the spacing betweenthe fingers may be based on a predetermined finger pitch dimension, theactual pitch defined by the fingers may vary slightly due to processvariations. Disclosed examples include both a vertical fin structure andthe horizontal finger structure over the fins, where the number of finsis equal to, or less than the number of fingers. Some embodiments mayinclude 5-50 fingers, with less than 20 fins. Other examples have 20-200fingers, and less than 20 fins. Other combinations of the number offingers and fins are within the scope of the disclosure.

In some examples, the resonator is formed of FinFET structures thatinclude a plurality of horizontally-extending semiconductor fins thatextend from a substrate, such as a silicon substrate, and form thetransistor active area, including the S/D regions of the transistor. TheFinFET gate structures (i.e. electrodes) include vertically-extendingconductive strips, or “fingers” as discussed above. An oxide or otherdielectric material (e.g. HfO2, SiC, SiN) is deposited between thefingers in what would be the S/D regions of the FinFET. However, in someexamples discussed further below, S/D regions are not actually formed inthe drive region since the resonator drive structure does notnecessarily function as transistors.

The fingers may be formed by “stacking” a plurality of conductivestructures (such as conductive metal layers) in a plurality of devicelayers. Some embodiments employ a constant finger pitch. In other words,a constant pitch is maintained between all of the device fingers. Inother examples, the finger pitch may vary. For instance, the device mayinclude some structures having a narrow pitch, while other structureshave a wider pitch such that resonator frequency may be selectable.

In accordance with further aspects of the disclosure, examples of theresonator structure may have varying numbers of resonator unit cells.For example, some embodiments have 1-20 unit cells. Further, the numberof unit cells per device may vary. For instance, some embodimentsinclude one device with multiple unit cells. Other examples may havemore than one device with multiple unit cells. Moreover, the fingerpitch and location of such unit cells may vary.

FIG. 1 is a block diagram conceptually illustrating portions of aresonator 100 in conjunction with some disclosed examples. The resonator100 includes a drive region 102 that, as will be discussed furtherbelow, includes a resonator structure including conductive fingersextending over semiconductor fins, where the resonator frequency istunable based on the finger pitch of the conductive fingers. The driveregion 102 receives an input drive signal Vdrive. The resonatorstructure of the drive region 102 resonates at a frequency based on thereceived drive signal, and the sense region 104 includes one or moresense transistors configured to sense the resonator signal generated bythe drive region 102, and output a sense signal isense.

FIG. 2 illustrates further aspects of an example of the drive region102. The drive region 102 includes fins 110 extending in a horizontal,or X direction. Conductive fingers 120 extend perpendicularly over thefins 110 in a vertical, or Y direction. In the example of FIG. 2 , thedrive region has fewer fins 110 (i.e. three fins) than fingers 120 (i.e.six fingers). As shown in FIG. 3 , a dielectric 130 is deposited betweenthe fingers 120 and over and around the fins 110.

FIG. 4 illustrates still further aspects of the resonator device 100. Asshown in FIG. 4 , the drive region 102 is adjacent the sense region 104,with the sense region 104 positioned immediately below the drive region102. As noted above, the fingers 120 of the drive region 110 are spacedapart based on a predetermined finger pitch 124 as shown in FIG. 4 . Aswill be discussed further below, the finger pitch defines the resonancefrequency of the drive region 102.

The sense region 104 includes one or more sense transistors 200. Thesense transistors 200 include a gate, which may be formed of a gateconductive strip similar to the fingers 120. In some examples, thefingers 120 of the drive region 102 include “dummy” fingers 122 that areformed along with the conductive fingers 120 of the drive region,extending parallel thereto. However, the dummy fingers 120 do notreceive the input signal Vdrive, but instead pass the resonator signalfrom the drive region 102 to the sensing region 104.

In the illustrated example, the sense transistors 200 are FinFETtransistors that include one or more sense transistor fins 210 extendingin the X direction, with the dummy fingers 122 extending over the fins210 to form the gates 220 of the sense transistors 200, as will bediscussed further below.

FIG. 5 is a flow diagram illustrating aspects of a method 300 of forminga resonator, such as the resonator 100 shown in FIG. 4 . At an operation302, fins are formed on or over a substrate. The fins may include thedrive region fins 110 and the sensing region fins 210, as shown in FIG.6 . The substrate may be made of silicon or other semiconductormaterials. Alternatively or additionally, the substrate may includeother elementary semiconductor materials such as germanium. In someembodiments, the substrate is made of a compound semiconductor such assilicon carbide, gallium arsenic, indium arsenide, or indium phosphide.In some embodiments, the substrate is made of an alloy semiconductorsuch as silicon germanium, silicon germanium carbide, gallium arsenicphosphide, or gallium indium phosphide.

In some examples, forming the fins in operation 310 includes forming apad layer and a hard mask layer on the substrate. A photoresist layer isformed on the hard mask layer, and the photoresist layer is patterned bya patterning process. The patterning process includes a photolithographyprocess and an etching process. The photolithography process includesphotoresist coating (e.g., spin-on coating), soft baking, mask aligning,exposure, post-exposure baking, developing the photoresist, rinsing anddrying (e.g., hard baking). The etching process includes a dry etchingprocess or a wet etching process

The pad layer is a buffer layer between the substrate and the hard masklayer. In addition, the pad layer is used as a stop layer when the hardmask layer is removed. The pad layer may be made of silicon oxide. Thehard mask layer may be made of silicon oxide, silicon nitride, siliconoxynitride, or another applicable material. In some other embodiments,more than one hard mask layer is formed on the pad layer. The pad layerand the hard mask layer are formed by deposition processes, such as achemical vapor deposition (CVD) process, high-density plasma chemicalvapor deposition (HDPCVD) process, spin-on process, sputtering process,or another applicable process.

After the photoresist layer is patterned, the pad layer and the hardmask layer are patterned by using the patterned photoresist layer as amask. As a result, a patterned pad layer and a patterned hard mask layerare obtained. An etching process is performed on the substrate to formthe fin structure 110, 210 by using the patterned pad layer and thepatterned hard mask layer as a mask. The etching process may be a dryetching process or a wet etching process. In some embodiments, thesubstrate is etched by a dry etching process. The dry etching processincludes using the fluorine-based etchant gas, such as SF6, CxFy, NF3 orcombinations thereof. The etching process may be a time-controlledprocess, and continue until the fins 110, 210 reach a predeterminedheight. In some other embodiments, the fin structures 110, 210 have awidth that gradually increases from the top portion to the lowerportion. After the fin structures are formed, the photoresist layer isremoved.

At operations 312 and 314 of FIG. 5 , drive fingers and a dummy fingerare formed over the fins. The drive fingers and the dummy finger mayinclude the drive region fingers 120 and the dummy fingers 122, as wellas the gates 220 of the sense transistors 200. FIG. 7 illustrates anexample of the arrangement of the fins 110, 210 and the fingers 120,including dummy fingers 122 and sense transistor gates 220. The dummyfingers 122 may further extend over the fingers 210 of the sensetransistors 200, thus forming gates 220 of the sense transistors 200. Inother examples, the conductive gate strips 220 of the sense transistors220 may be separately formed and electrically connected to the dummyfingers 122. The fingers 120, 122 and sense transistor gate 220 can beformed, for example, as typical FinFET gate structures, such aspoly-silicon gate, metal gate, or the like.

The fingers 110, 210, which may be conventional FinFET gate structures,may include a gate dielectric layer and a gate electrode layer. The gatedielectric layer is made of dielectric materials, such as silicon oxide,silicon nitride, silicon oxynitride, dielectric material(s) with highdielectric constant (high-k), or combinations thereof. The gatedielectric layer is formed by a deposition process, such as chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), high density plasma CVD (HDPCVD), metal organic CVD(MOCVD), or plasma enhanced CVD (PECVD).

In some embodiments, the fingers (i.e. gate structures) 110, 210 aremade of conductive materials, and may be a polysilicon gate (poly ordummy gate) or metal gate (replacement metal gate). For example, thegate electrode layer 210 may be formed by a deposition process, such aschemical vapor deposition (CVD), physical vapor deposition (PVD), atomiclayer deposition (ALD), high density plasma CVD (HDPCVD), metal organicCVD (MOCVD), or plasma enhanced CVD (PECVD).

Returning to FIG. 5 , a dielectric material 130, such as oxide, isformed in the S/D regions of the drive region fins 110 in operation 316.In some embodiments, a contact etch stop layer (CESL) is formed beforethe dielectric structure 130 is formed. In example embodiments, thedielectric material may include silicon oxide, hafnium oxide, siliconcarbide, silicon nitride, and/or other applicable dielectric materials.Moreover, the dielectric 130 my include multilayers made of multipledielectric materials.

As noted above, the drive region includes the fins 110 and fingers 120,122 (i.e. gate structures) in accordance with CMOS FinFET structures. Insome embodiments, S/D structures 130 are formed by growing a strainedmaterial on the fins 110, 210 by an epitaxial (epi) process. Theepitaxial process may include a selective epitaxy growth (SEG) process,CVD deposition techniques (e.g., vapor-phase epitaxy (VPE) and/orultra-high vacuum CVD (UHV-CVD)), molecular beam epitaxy, or othersuitable epi processes. However, as discussed further below, the fingers120 are configured to receive a drive signal whereby the drive region102 functions as a resonator with a resonant frequency that is tunablebased on the finger pitch. As such, S/D structures are not necessarilyformed in the fins 110 of the drive region 102 (i.e. there is no S/Depi).

FIG. 8 is a section view taken along line Y2 of FIG. 4 , showing thefins 110 extending over the substrate 112. The fingers 120 are situatedover the fingers 110. The section view of FIG. 8 illustrates one of thedummy fingers 122, which extends over the sense transistor fins 210,forming a gate 220 of the sense transistor 200. The dielectric 130 issituated on the S/D regions of the fins 110 in the drive region 102.

FIG. 9 is a section view taken along line X2 of FIG. 4 , illustratingportions of the sensing region 104. One of the fingers 210 forming thesense transistors 200 is shown with its source S and drain D regions,and the sensing transistor conductive gate strips 220. Thus, the sensingtransistors 200 may be standard FinFET transistors, with source anddrain nodes and a channel formed between the source and drain nodes. Asnoted above, in the illustrated example the dummy fingers 122 extendover the sensing transistor fins 210, forming the gates 220 thereof.

FIG. 10 is a section view taken along line Y1 of FIG. 4 , showing one ofthe fingers 120 over the fins 120 of the drive region 102. The oxide 130is situated in the S/D region of the fins 110. FIG. 11 is a section viewtaken along line X1 of FIG. 4 , illustrating a portion of the driveregion 102. The fingers 120, including the dummy fingers 122, extendover the fingers 110 extending from the substrate 112. The oxide 130 issituated in the S/D regions of the fingers 110.

Returning to the method shown in FIG. 5 , operation 318 includesconnecting a voltage input terminal configured to receive a drive signalto the plurality of conductive drive fingers, and operation 320 includesconnecting the dummy finger to an output terminal configured to output asense current. More particularly, FIG. 12 is a circuit diagram of anexample of the resonator 100 disclosed herein. The fingers 120 areelectrically connected to voltage input terminals 140 that areconfigured to receive opposite polarity drive voltage signals+Vdrive/-Vdrive. As shown in the example of FIG. 12 , pairs of thefingers 120+, 120- are connected to the input terminals 140 to receivethe respective +Vdrive, -Vdrive, drive signals, which are RF signals insome embodiments. The input signals +Vdrive, -Vdrive received by theinput terminals 140 connected to the respective fingers 120+, 120- (i.e.gates) cause the drive transistor structures in the drive region 102 toresonate. Dummy gates 122+, 120- of the sense transistor structures inthe sensing region 104 are connected to output terminals 142 to provideopposite polarity sense currents +isense, -isense.

FIG. 13 is a circuit diagram illustrating further aspects of an exampleof the resonator 100. In FIG. 13 , a DC drive voltage VDC-drive isconnected to inductors 150 a, 150 b respectively connected to thevoltage input terminals 140 for the fingers 120+, 120- to provide theopposite polarity drive voltage signals. Alternating opposite polarityperiodic drive signals +1/2vdrive, –1/2vdrive are additionally connectedto the voltage input terminals 140 of the respective fingers 120+, 120-through resistors 152 and capacitors 154. The periodic drive signals+1/2vdrive, -1/2vdrive are RF signals in some examples. The dummyfingers 122+, 122- are connected to output the sense current isenseacross a load resistor 164 connected to inductors 162, which areconnected to a DC sense voltage VDC-sense. In the example shown in FIGS.12 and 13 , the fingers 120+, 120- are illustrated as gate terminals oftransistors (i.e. FET schematic symbols are shown in FIGS. 12 and 13 ).However, as discussed hereinabove, in some examples source and drainregions of the fins 110 in the drive region 102 are not necessarilyformed. Instead, the source and drain regions of the fins 110 are filledwith a dielectric material, such as oxide (i.e. there is no source/drainepi).

FIGS. 14-16 illustrate examples of different arrangements of theconductive fingers 120 and dummy fingers 122, which may form the gates220 of the sensing transistors 200. In some examples, such as thatillustrated in FIG. 14 , the dummy fingers 122 are situated adjacent oneanother. The dummy fingers 122 extend from the drive region 102 to thesensing region 104 and form the gates of the sense transistors 200. Inother examples, the dummy fingers 122 are separated from one another byfingers 122 of the drive region 102. In FIG. 15 , the dummy fingers122+, 122- are separated by one pair of the fingers 120-, 120+. In FIG.16 , the dummy fingers 122+, 122- are on opposite ends of the resonator100, and as such, are separated by two pairs of the fingers 120+, 120-.Still further, it is noted that the disclosure is not limited toillustrated arrangement where the sense region 104 is immediatelyadjacent the drive region 102. In other embodiments, the sense region104 (i.e. sense transistors 200) may be located separate from the fins110 and fingers 120, 122 of the drive region 102.

In some examples, the fingers 120 may include a conductive gate strip,such as a poly gate. Further, a plurality of conductive layers may be“stacked” over the conductive gate strips to form the fingers 120 anddummy fingers 122. FIGS. 17-22 illustrate various examples. Morespecifically, FIG. 17 is a section view in the same orientation as thatshown in FIG. 11 (i.e. line X1 in FIG. 4 ), and FIG. 18 is a sectionview in the same orientation as that shown in FIG. 10 (i.e. line Y1 inFIG. 4 ). A plurality of conductive layers, such as metal layers 170,are over the conductive fingers 120 and electrically connected thereto.The metal layers 170 may stack up to respective conductive connectionbumps 172. The conductive gate strips of the fingers 120 together withthe stacked metal layers 170 thus form a finger height 174 dimension. Insome examples, the finger height 174 is greater than a fin height 114.

FIG. 19 is a section view in the same orientation as that shown in FIG.9 (i.e. line X2 in FIG. 4 ), and FIG. 20 is a section view in the sameorientation as that shown in FIG. 8 (i.e. line Y2 in FIG. 4 ). Metallayers 170, which may stack up to the respective conductive connectionbumps 172, are over the gate strips 220 of the sensing transistors 200and electrically connected thereto.

In the examples shown in FIGS. 17-20 , the fingers 120 have a constantpitch. In other words, each of the fingers 120 define the sameseparation therebetween. In other examples, the finger pitch may vary.FIG. 21 is a section view in the same orientation as that shown in FIG.17 (i.e. line X1 in FIG. 4 ). In the in the example of FIG. 21 , thefingers 120 define a wider pitch 124 b as compared to the narrower pitch124 a defined by the fingers 120 in FIG. 17 . Further, in FIGS. 17 and21 , all of the fingers 120 have the same pitch (i.e. all of the fingers120 are separated by the same distance).

FIG. 22 is a section view in the same orientation as that shown in FIGS.17 and 21 (i.e. line X1 in FIG. 4 ), illustrating an example in whichthe device 100 includes fingers 120 with different pitches 124 a, 124 b.More specifically, the pair fingers 120 a shown on the left side of FIG.21 define a narrow pitch 124 a, while the pair of fingers 120 b shown onthe right side of FIG. 21 define a wide pitch 124 b. As noted above, thefrequency of the resonator 100 may be tuned by varying the finger pitch124.

FIG. 4 discussed above illustrates a single resonator device 100 thatincludes the drive region 102 and the sensing region 104. The disclosureis not listed to a single resonator provided for a device. For instance,FIG. 23 illustrates a device 100 that includes two resonator unit cells101 a and 101 b. Each of the unit cells 101 a, 101 b includes a driveregion 102 and a sensing region 104, which may be constructed asdescribed hereinabove. FIG. 24 illustrates a device 100 that includesthree unit cells 101 a, 101 b and 101 c, while FIG. 25 illustrates yetanother example that includes four unit cells 101 a, 101 b, 101 c and101 d. Further examples may include additional unit cells 101. Forinstance, some examples may include up to 20 unit cells, though thedisclosure is not limited to any particular number of unit cells for theresonator 100.

In the example shown in FIGS. 23-25 , each of the unit cells 101 a, 101b, 101 c, 101 d may define a constant finger pitch. FIG. 26 illustratesyet another example in which two resonator devices 100 a and 100 b areprovided. The first resonator device 100 a is similar to that shown inFIG. 23 , including two unit cells 101 a and 101 b that each have adrive region 102 and a sensing region 104. In the example of FIG. 26 ,each of the unit cells 101 a and 101 b define a narrow finger pitch,such as the narrow finger pitch 124 a shown in FIGS. 17 and 22 . Thesecond resonator device 100 b has a single unit cell 101 c, which alsohas a drive region 102 and a sensing region 104. The unit cell 101 c,however, has a wide finger pitch, such as the wide finger pitch 124 bshown in FIGS. 21 and 22 .

Moreover, in the example shown in FIG. 26 , both resonator devices 100 aand 100 b are arranged with their drive regions 102 situated above thesensing regions 104 as shown in the drawing. FIG. 27 illustrates anotherexample, in which the orientation of the resonator unit cells may bevaried. As shown in FIG. 27 , the first resonator device 100 a isarranged as shown in FIG. 26 , with its drive region 102 positionedabove the sensing region 104. As with the resonator device 100 a shownin FIG. 26 , the resonator device 100 a of FIG. 27 has two unit cells101 a and 101 b that each have a drive region 102 positioned above asensing region 104, and each of the unit cells 101 a and 101 b defines anarrow finger pitch, such as the narrow finger pitch 124 a shown inFIGS. 17 and 22 .

In the example of FIG. 27 , however, the second resonator device 100 b(which has a single unit cell 101 c) is inverted. In other words, thesensing region 104 is positioned above the drive region 102 in theresonator device 100 b shown in FIG. 27 . As shown in FIG. 27 , thisfacilitates sensing transistor structures 200 in the sensing regions 104of the resonator devices 100 a and 100 b to have some common fins 210,potentially resulting in a smaller device. Further, the unit cell 101 chas a wide finger pitch, such as the wide finger pitch 124 b shown inFIGS. 21 and 22 .

FIG. 28 is a flow diagram illustrating an example of a resonator method350 in accordance with the present disclosure. Referring to FIG. 28 inconjunction with Figures discussed above, at an operation 360 aplurality of semiconductor fins 110 are provided that extend in a firstdirection X. A plurality of conductive drive fingers 120 are providedover the fins 110, which extend in a second direction Y. The fins 110and fingers 120 are components of the drive region 102 of the exampleresonator devices 100 discussed above. At operation 364, an inputsignal, such as the +Vdrive, -Vdrive, +1/2vdrive, and -1/2vdrive inputsignals, is applied to the plurality of conductive drive fingers 120. Adummy finger 122 is further provided over the fins, which extends in thesecond direction as indicated at operation 366. At operation 368, thedrive signal is applied from the conductive drive fingers 120 to a gate220 of a sensing transistor 200 via the dummy finger 122. As discussedabove, a first polarity input signal +Vdrive may be applied to a firstone of the conductive drive fingers 120+ while a second polarity inputsignal -Vdrive may be applied to a second one of the conductive drivefingers 120+. In some examples, the number of semiconductor fins is lessthan or equal to the number of conductive drive fingers (i.e. fins ≤fingers). As noted above, the resonator output frequency is tunable byvarying the finger pitch 124 of the conductive drive fingers 120.

Thus, with some aspects of the present disclosure, a resonator deviceincludes a substrate with a first number of fins extending over thesubstrate. The fins extend along the substrate in a first direction(i.e. X direction). A second number of conductive fingers are providedover the fins, which extend in a second direction perpendicular to thefirst direction (i.e. Y direction). The first number is less than orequal to the second number. The conductive fingers are configured toreceive an input signal such that the conductive fingers resonate at anoutput frequency. The conductive fingers are spaced apart from onanother based on a predetermined finger pitch, and the output frequencyis based on the finger pitch.

In accordance with further aspects of the disclosure, a resonator devicehas a drive region that includes a plurality of fins extending parallelto one another in a first direction (i.e. X direction). The fins arespaced apart from one another in a second direction perpendicular to thefirst direction (i.e. Y direction). A plurality of dielectric structuresare situated in gaps formed between adjacent ones of the drive fins, anda plurality of conductive drive fingers are over the fins. Theconductive drive fingers extend in the second direction and areconnected to receive a periodic input signal. The drive region includesa dummy finger that is not connected to receive the periodic inputsignal. A sense region includes a sense transistor having a source, adrain and a gate. The gate is connected to the dummy finger.

In accordance with still further aspects of the present disclosure, amethod of forming a resonator includes forming a plurality ofsemiconductor fins extending in first direction (i.e. X direction) overa substrate and a plurality of conductive drive fingers over the finsextending in a second direction (i.e. Y direction). A dummy finger isformed over the fins that extends in the second direction. A voltageinput terminal configured to receive a drive signal is connected to theplurality of conductive drive fingers, and the dummy finger is connectedto an output terminal configured to output a sense current.

This disclosure outlines various embodiments so that those skilled inthe art may better understand the aspects of the present disclosure.Those skilled in the art should appreciate that they may readily use thepresent disclosure as a basis for designing or modifying other processesand structures for carrying out the same purposes and/or achieving thesame advantages of the embodiments introduced herein. Those skilled inthe art should also realize that such equivalent constructions do notdepart from the spirit and scope of the present disclosure, and thatthey may make various changes, substitutions, and alterations hereinwithout departing from the spirit and scope of the present disclosure.

What is claimed is:
 1. A device, comprising: a substrate; a first number of fins over the substrate, the fins extending along the substrate in a first direction; a second number of conductive fingers over the fins, the conductive fingers extending in a second direction perpendicular to the first direction, the first number being less than or equal to the second number, the conductive fingers configured to receive an input signal such that the conductive fingers resonate at an output frequency; and wherein the conductive fingers are spaced apart from one another based on a predetermined finger pitch.
 2. The device of claim 1, further comprising: a dummy conductive finger extending in the second direction that is not configured to receive the input signal; and a sense transistor having a gate connected to the dummy conductive finger.
 3. The device of claim 2, wherein the sense transistor comprises: a sense fin extending along the substrate in the first direction, the fin including a source node and a drain node and a channel between the source and drain nodes; a conductive gate strip over the sense fin extending in the second direction.
 4. The device of claim 3, wherein the dummy conductive finger forms the conductive gate strip on the sense fin.
 5. The device of claim 1, wherein the fins do not have source/drain epitaxial thereon.
 6. The device of claim 1, further comprising a plurality of dielectric structures situated in respective gaps formed between the fins.
 7. The device of claim 1, wherein the conductive fingers each include a conductive gate strip and a plurality of metal layers over and electrically connected to the conductive gate strip.
 8. A device, comprising: a drive region including: a plurality of fins extending parallel to one another in a first direction, wherein the fins are spaced apart from one another in a second direction perpendicular to the first direction; a plurality of dielectric structures situated in gaps formed between adjacent ones of the fins; a plurality of conductive drive fingers over the fins, the conductive drive fingers extending in the second direction and connected to receive a periodic input signal; a dummy finger that is not connected to receive the periodic input signal; and a sense region including: a sense transistor having a source, a drain and a gate, the gate connected to the dummy finger.
 9. The device of claim 8, wherein the conductive drive fingers each include a conductive gate strip and a plurality of metal layers over and electrically connected to the conductive gate strip.
 10. The device of claim 8, wherein the conductive drive fingers are spaced apart based on a predetermined finger pitch therebetween.
 11. The device of claim 8, wherein there are more of the conductive drive fingers than the fins.
 12. The device of claim 8, further comprising: first and second sense transistors including the sense transistor, the first and second sense transistors including a fin extending in the first direction and having respective first and second source/drain nodes of the first and second sense transistors; and first and second dummy fingers including the dummy finger, the first and second dummy fingers forming respective first and second gate terminals of the first and second sense transistors.
 13. The device of claim 12, wherein the first and second dummy fingers are adjacent one another.
 14. The device of claim 8, wherein the fins do not have source/drain epitaxial thereon.
 15. The device of claim 8, wherein the conductive drive fingers are configured to receive an RF drive signal, and wherein the gate of the sense transistor is configured to provide an output signal from the dummy finger based on the RF drive signal.
 16. The device of claim 8, wherein the drive region includes a first group of the plurality of fins spaced apart from one another based on a first predetermined finger pitch, and a second group of the plurality of fins spaced apart from one another based on a second predetermined finger pitch different from the first predetermined finger pitch.
 17. A method, comprising: forming a plurality of semiconductor fins extending in first direction over a sub strate; forming a plurality of conductive drive fingers extending in a second direction over the fins; forming a dummy finger extending in the second direction over the fins; connecting a voltage input terminal configured to receive a drive signal to the plurality of conductive drive fingers; and connecting the dummy finger to an output terminal configured to output a sense current.
 18. The method of claim 17, wherein connecting the voltage input terminal includes connecting a first voltage input terminal to a first one of the conductive drive fingers, the first voltage input terminal being configured to receive a first polarity input signal, and connecting a second voltage input terminal to a second one of the conductive drive fingers, the first voltage input terminal being configured to receive a second polarity input signal.
 19. The method of claim 17, wherein forming the plurality of conductive drive fingers includes spacing apart the plurality of conductive drive fingers in the second direction based on a predetermined finger pitch.
 20. The method of claim 19, the predetermined finger pitch is based on a desired output frequency of the sense current. 